CARBON DISTRIBUTIO:\l 1:\1 SOIL PARTICLE-SIZE FRACTIO:\,S ALO:"iG A:\I ALTITUDINAL
GRADIE:\IT 1:\1 THE TRA:\IS\lEXICAN VOLCA:\IIC BELT
1
1
SARA COVALEDA , JUAN F. GALLARD0 , FELIPE GARCiA-OLIVA 2, CHRISTIAN PRAT 2 ,
MIGUEL BRAVO.), & HOLGER KIRCHMANN~
/C. S. I.
c., Aptado ]57, 501011/0/7('(137071 (SIJoil7).
~ I.R. D./INIFA?, Morelia (vlichoacan. Mexico).
CIF:CO, GNA/vl. COli/PUS Morclia I.\lnico)
, Sv.edish Universitv ojAgriclllrll/'U1 Sciences, LjJIJ,'olo (Swede/7)
3
Corresponding author: jgallardCo usal.es
Abstract
In this work. the impact of land use and forest degradation on changes of soil C contents was
evaluated. The C distribution in particle-sizes fractions of two types ofvolcanic soils tAndosols and Acriso!s)
located in a topo-sequenee were determined after dispersion and the coarse sand. fine sand. silt. clay. and
particulatc organic matter (POM) fractions were analyzed. Acrisols, due to their high clay content,
accumulated about 60% of the SOC in the clay fraction whereas Andosols stabilized C mostly in the silt
fraction. The PO\!! was the most sensitive fraction to changes of land use managements and could be a useful
indicator of long-term changes in soil C contents. The C contents in clay-, silt-, and POM fractions decreased
in the Andosols with forest degradation,
Introduction
The association of soil organic matter (SO\1) with soil-mineral fractions is an important factor
controlling the storage and mineralization of SOM (Feller & Bcarc. 1997). There arc a number of papers
dealing with the organic material-inorganic fractions association in temperate soils. but less information is
available for tropical soils and. specifically. volcanic soils. The aim of this work was to determine how land
use and forest degradation affect the content and distribution of C in soil particle-sizes in a topo-scqucncc,
including two types of volcanic soils' Andosols and Acrisols. Such knowledge may enable a better
understanding of the SOM dynamics in both types of soils. abundant in the Transmcx ican Volcan ic Belt.
:VI aterials and :VI ethods
The study site is located at the Atccuaro catchment (Michoacan. Mexico). The most representative
land-use systems along an altitudinal gradient were identified. The upper parts were dominated by Andosols:
grasslands (P l . 2615 m): mixed pine-oak forests. increasing degradation down-slope (P2. 2496 m: P3. 241 I
m: P6. 2320 m): fuel-wood area (P4. 2370 m): and agricultural lands (PS. 2330 m). At the piedmont.
dominated by Acrisols there were cultivated fields (PS. 2211 1 m) and grasslands (P9. 2290 m). Composite
soil-samples were taken from the upper -10 cm. The fractionation procedure consisted of three steps:
sonication to completely disrupt aggregates. wet sicving to segregate coarse particles (> (l.05 mm). and
centrifugation to separate silt from clay. The fractions obtained were: coarse sand (CS). fine sand (FS). silt
(ST). and clay (CY). Particulatc organic matter (PO\!!) was separated from CS (POM-CS) and FS (POMFS). Soil organic C (SOC) and total N (Nt) were determined by dry combustion. Differences among soil
types and land uses were subjected to either one-way ANOVA or the Kruskal-Wallis non-parametric tcst.
Results and Discussion
The results of SOc. soil C/N ratio and the C content and eN ratio of the separated particle-size
fractions arc reported in Table I. SOC and C contents of ST. FS and CS particle-size fractions were
significantly lower in Acrisols (P7 and PII) than in Andosols (PI. P2. P3. P4. P5. and P6). Accumulation of
SOM is a characteristic property of Andosols (Dahlgrcn et al., 2(04). For that. the two groups were evaluated
separately.. In Acrisols, 60% of the total SOl' was associated with CY indicating a strong linkage. 30% with
ST. 1'Yo with the sand tractions. and less than 10% was present as POM. The content of SOC was lower in
the agricultural land. which contained less POM both in absolute and relative terms. The C/N ratio in the
clay fraction was less than 16. indicating that the C associated to this fraction was more hurnificd and
stabilized and less subjected to mineralization. On the contrary. the C 1\ ratio of SOM associated to the sand
fractions and to the POM ranged from 17 and 50 and is probably easily mineralizablc (Christcnscn. 1992).
Table I. Soil organic carbon and C distribution in soil particle-size fractions
Site
Fine sand (FS) Coarse sand (CS)
PO\I-CS
POM-FC
-I
(mg C rrb soil )
07a
1.1 a
2.7a
1.7b
PI
5S.6a
27.6ad
J2.7ac
O.()a
69.1 b
17.8b
21.9a
P2
1JOb
41.6b
1.6a
P'.1
IO.-Ia
0.7a
S2.Jc
J6.7ac
50.1 c
O.Sa
S.2c
I .o,
0.6a
P-I
57.Ja
22.Sd
3X.3a
S.5c
5.5ab
P~
0.9a
1S.6d
20a
2.7b
J 5.Od
2J4d
O.Sa
O.Sa
P6
50.5a
21.1d
J54a
OSa
-I. Ia
-I.Jb
P7
I-I.-Ia
12.6a
0.1 a
o 7a
0.6a
67a
o 1a
lOb
0.2a
1.6a
PS
22Sb
18.Sa
10.-1a
0.1 a
'Y!) referred to SOC
Recovery
PI
3~.2a
5J-Ia
I.Jab
IJa
J-Ib
:'.Oa
103
29.2b
-IS.6a
OAb
152a
12.-Ia
P2
lOO
12a
07a
9.-Ia
7.Sa
0.6b
PJ
107
J4.:'b
-I7.2a
P4
2S.Sb
7.1a
6.:'a
100
51.1 a
24a
0.9'lb
-IS.()a
P:,
U\a
-I.Ia
1.6a
:'.6b
96.8
JS4a
1.2ab
62a
P6
lOO
J l.7b
:'J.2a
1.2a
6.-Iab
60.()a
2.9a
_r~.3a
P7
0.7a
3.3a
100
O.Ja
:,2b
0.6a
PS
100
58Aa
J2.Ja
04a
3.2a
C/N ratio
14()
12.S
17.5
16J
2S.-I
4-1.J
Pi
II.S
29.J
IH
24.1
29.S
33.5
~7.~
P2
14.:'
' - ')
27]
.)J._
140
4S.2
P3
14.:'
27.:'
272
J4()
J06
P-I
15.7
50 0
:'1\.6
96.:'
1S.J
J6.()
10.9
IS.7
19.3
267
PS
114
204
4()O
277
26.1
29S
:'79
P6
13.9
12.7
1S.2
10S
IS.8
29.6
275
J7.6
P7
I 1.8
S] .0
25:'
PS
15 0
112
IS.S
23.7
J02
(*Different lcncrs \\ ithin columns indicate signific'll1ce at P < 0.0:> level for each sue ofthe same soil ivpc )
SOC
Clay (C\)
Silt (ST)
In the Andosol sites. around 50° ° of the SOC content was linked to silt. 30'Yo to clay. less than 5° 0 to sand
fractions and 5 0 0 to POM. The distribution ofC in particle fractions was significantly affected by land use. i\
loss of POM in the fine-sand fraction and an increase of C in the mineral fine-sand and clay fraction was
observed in the agricultural land. which \\as also found by Cambardclla & Elliott (1992). The Cl\; ratios of
the bulk organic material, silt- and POM of the fine-sand fraction were higher in the forest than in the
grassland and agricultural land. Significant differences were found in C associated to clay. silt and POM
between the forest sites. Highest values were found in the better preserved-areas (P2 and P3) and lowest C
contents were present in the more degraded forest sites (P4 and PO) as a consequence of human activities,
Conclusions
In Acriso!s. most organic matter was stabilized in the clay-sized fraction as a consequence of their high clay
content. in spite that Acrisols has a very 10\\ er C content than the Andoso!s, Furthermore. POM in the coarsesand fraction was most sensitive to land use management and may be useful indicator of land use
management in Acriso!s. In Andosols, C was mostly linked to the silt-sized fraction. Forest degradation could
be linked to a decrease of C in clay-. silt- and POM fractions in these soils.
References
Cambardclla. CA. & ET Elliott. 1992.. Soil s.: S(J(' .-1117. J 56 777-7S3
Christcnscn. HT 1992. Advance, in Soil Scicnc« 20: ]-90
Dahlgrcn. R.A .. \;1. Saigusa, &
r.c. Lgolini. 200-1 . . ulvanccs
ill . Jgml7olll.1' 82: 11 J-I S2.
Feller. C & \;1.H. Bcarc, 1997. Phvsical control of soil organic matter dynamics in the tropics. Geodenna 79: 69-116 ..
Covaleda S., Gallardo J.F., Garcia-Oliva F., Prat Christian, Bravo M., Kirchmann H
Carbon distribution on soil particle-size fractions along an altitudinal gradient
in the transmexican volcanic belt.
s.l. : s.n., 2007, 2 p. multigr. International Symposium on Organic Matter
Dynamics in Agro-Ecosystems, Poitiers (FRA), 2007/07/16-19.